1. Field of the Invention
This invention relates generally to a refrigerating system having an electric-powered compressor, and more specifically to a refrigerating system which is designed to prevent failure or damage due to unwanted changes of compression level caused by the drop or rise of the ambient temperature of the refrigerating system.
2. Description of the Prior Art
In general, a refrigerating system comprises a compressor driven by electric energy, a condenser to which refrigerant compressed by the compressor is fed, a capillary tube provided on the downstream side of the condenser, an evaporator provided on the downstream side of the capillary tube, the refrigerant evaporated in the evaporator being compressed again in the compressor.
Particularly, when the compressor is a compressor of the electrical vibration type, the vibrating strokes of the electrical vibration type compressor often increase unwantedly as the ambient temperature of the refrigerating system lowers, leading to damages of the valve chest. Refrigerating systems of the abovementioned type are often used for refrigerators on board leisure vehicles (such as camping cars). When such a leisure vehicle is parked near the skiiing ground, the aforementioned phenomenon often occurs as the atmospheric temperature drops. That is, while the refrigerator on board the leisure vehicle is operated at the room temperature in the vehicle, the condenser connected to the compressor of the refrigerator, which is exposed to the outdoor temperature, is cooled to as low as -30.degree. C., in extreme cases. As a result, most of the refrigerant is stored in liquefied state in the condenser, and trickles down in small quantities to the evaporator where the refrigerant is, immediately after adiabatically expanded, fed to the condenser by the compressor. This brings the gas pressure in the evaporator and the compressor to almost a vacuum, causing the vibrating stroke of the electrical vibration type compressor to increase unwantedly to such an extent that the valve chest is eventually damaged.
Needless to say, the electrical vibration type compressor is designed to maintain the natural vibration cycle, or frequency, of the mechanical vibration system, which is determined by the coefficient of elasticity of the refrigerant gas and the spring constant of the mechanical vibration system, and the vibration cycle, or frequency of the electrical vibration system for driving the mechanical vibration system at a resonating state, whereever possible. Particularly, the refrigerating system constructed so as to properly maintain the resonance by changing the vibration cycle of the electrical vibration system in accordance with changes in the natural vibration cycle of the mechanical vibration system is directly and sensitively, affected by the aforementioned increase in the vibration stroke because, even when the natural vibration cycle of the mechanical vibration system is changed due to decreases gas pressure of the refrigerant, the vibration cycle of the electrical vibration system, or the vibrating frequency of alternating voltage, is changed in accordance with the change of the natural vibration cycle to maintain the resonance. It was also found that, when a refrigerating system of this type is driven at an elevated ambient temperature, the windings of the compressor tend to be burned out unwantedly.